This paper describes an industrial plant layout system with an intelligent interactive user-interface. This system offers a powerful design environment, in which a designer can concurrently draw and check a layout plan, which can not be realized on a conventional plant layout CAD system. The major function of the system is the automatic constraint checking of each designer’s drafting action. This function is achieved by the integration of a geometric modeler, frame representation, and production rules. The geometric modeler is used for extracting the information for data updating and constraint checking from graphical objects, which are directly manipulated by a designer. Frame representation is used for representing the attributes of the equipments and the areas, and these attributes are handled by production rules. Production rules are used for representing the constraint checking and data updating procedures, and can be executed as required.